The constant increase in waste generation worldwide is accompanied by an increasing need to provide for proper waste disposal. In the natural resource mining industry this trend is exemplified by the need to find and provide practicable and efficient technologies for the proper disposal of oil field and other such solid and liquid wastes that are not only cost-effective, but also environmentally sound. Such technologies often involve special methods and equipment for injecting and disposing of the waste in underground reservoirs such as subterranean cavities and salt caverns. Hence, technologies exist for the disposal of various types of wastes in underground reservoirs, and many techniques have been developed for creating and providing caverns in subterranean formations. Thus, for example, U.S. Pat. No. 4,435,290, of Lindörfer et al., discloses a process for the temporary storage and treatment of certain liquid wastes in an underground salt cavern, whereby acidic wastes are pumped underground and neutralized, then allowed to stand to separate their components by gravity. Part of the overlying light phase (such as an oil phase) is subsequently pumped out and the underlying aqueous heavy phase treated to precipitate the heavy metals, the heavy-metal-free overlying salt solution is then pumped out and the process steps repeated as necessary. The volume of the cavern can be maintained by pumping out the corresponding amount of salt solution. The excess salt solution may be discharged into the sea or put back into the caverns. In U.S. Pat. No. 4,577,999, Lindörfer et al., improve this technique by chemically treating liquid waste above ground to make it more “pumpable”.
U.S. Pat. No. 4,488,834, of Hooper et al., claims a method for creating a special type of underground storage from a salt deposit by solution mining. The method consists in drilling a first well into the salt deposit and circulating raw water through it, then evacuating the water and injecting the material to be stored (which includes waste material) into the mined cavity, then sealing the cavity. A second well is then drilled on top of the first well and raw water again circulated and evacuated from the thus formed cavity, which is subsequently injected with the waste material and plugged. Means are provided to withdraw the injected material from storage. Multiple stacked storage cavities can be created in this fashion in which the first cavity may be a relatively small cavity that is easy to create and (if desired) larger storage cavities may be made thereafter from the same well on an as-needed basis.
U.S. Pat. No. 4,576,513, of Lindörfer et al., discloses a process for the terminal storage and treatment of certain liquid wastes in underground salt caverns. This is a companion patent to U.S. Pat. No. 4,435,290, in which the specific gravity of the waste liquid phase is increased by the addition of certain magnesium salts so as to convert the liquid phase into a paste-like consistency and thereby minimize convergence (volume contraction) of the salt caverns. Adsorbents (vermiculites, perlites and the like) are also used to increase the specific gravity. The idea is to narrow the difference between the specific gravity of the salt mineral of the cavern walls and the specific gravity of the liquid waste contained within the walls. Narrowing this difference eliminates or minimizes the undesirable convergence. The caverns are sealed after substantial solidification of the wastes has taken place.
U.S. Pat. No. 4,596,490, of Van Fossan et al., teaches a method of making underground storage chambers within salt formations by solution mining techniques in order to store brine- or water-soluble fluid materials, such as caustic soda, anhydrous ammonia and ethylene dichloride. U.S. Pat. No. 4,692,061, of Lindörfer et al., addresses the disposal of particulate solid waste materials in an underground salt-enclosed cavity that contains rock salt solution. The novelty of the method revolves around the treatment of the solid waste materials with a dust suppressant and solidifying the water that may be present in the dust suppressant. Other chemicals are added to the injected materials in order to best convert them to a “pumpable” state. U.S. Pat. No. 4,906,135, of Brassow et al., claims an elaborate method and apparatus for the disposal of hazardous wastes in salt domes whereby the wastes are first transferred to a “chemical solidification unit” to be solidified, then sent down to a salt cavern by means of injection tubes under controlled conditions; while U.S. Pat. No. 4,886,393, of Jahn-Held et al., addresses ways of pretreating a solid waste so that it may be injected by gravity into underground salt caverns via a down pipe.
U.S. Pat. No. 5,310,282, of Voskamp, discloses a method for the recovery of hydrocarbons from hydrocarbon-contaminated drilling muds that are stored in salt cavities. Brine is displaced from the cavities by the contaminated drilling muds that, after being injected, separate into a relatively dense component that gravitates to the bottom and a relatively light hydrocarbon component that rises through the brine and accumulates at the top of the cavity. The preferred cavities are located in anhydride formations that cause the solution-mined caverns to exhibit natural baffle-like anhydride ledges that provide a tortuous flow path thereby facilitating the separation of the hydrocarbons.
U.S. Pat. Nos. 5,589,603 and 5,734,988, both of Alexander et al., cover systems for the injection disposal of oil field waste in naturally occurring subterranean formations, whereby the formations are penetrated with a borehole, a slurry of solid material is then made at the surface of the earth and sent into the formation through the borehole while reducing the slurry pressure at the surface so that the pressure of the slurry inside the formation is less than the formation fracture pressure. U.S. Pat. No. 5,669,734, of Becnel, Jr. et al., describes an improved process for creating large underground storage caverns in domal salt deposits found in certain areas, such as the northeastern part of the United States, where the normal temperature of the water used for solution mining is relatively low. The process involves clarifying and using warm brine, produced on-site by solution mining the salt deposit, as the heating medium in an indirect-heating heat exchanger in order to preheat fresh water from local reserves. The preheated water is further heated, injected and circulated under controlled conditions through one or more caverns to maximize heat recovery efficiencies. The heat-depleted brine can be injected into disposal wells or used in chemical plants that require brine.
U.S. Pat. No. 5,863,283, of Gardes, discloses a system for disposing of hazardous wastes in deep underground formations. A special borehole configuration and sealed liner are provided. U.S. Pat. No. 6,002,063, of Bilak et al., claims a method and the equipment for the subterranean deep injection disposal of solid waste, in slurried form, within rock formations. A cased injection well is employed to inject the pressurized slurry of the waste material in a carrier liquid under controlled conditions. Many operational parameters are stipulated, and criteria for selecting the geological formation are offered and discussed.
U.S. Pat. No. 6,137,028, of Snow, discloses a method for the disposal of certain radioactive oil field waste material in subterranean salt formations. The method entails the drilling of two interconnected wells into a salt formation and the subsequent injection of the waste material, in aqueous slurry form, into the first well, allowing the waste solids to be deposited at the bottom of said well, and then withdrawing the slurry water from the formation through the second well. In another embodiment, fresh water is injected into the first well while withdrawing the resulting brine from the second well so as to create a salt cavern. The waste material is then slurried with salt water and injected through the first well, in slurry form, into the salt cavern. The waste solids are subsequently allowed to be deposited at the bottom of said salt cavern, and the slurry salt water is then withdrawn from the formation through the second well.
While the technologies described in these patents serve to address a number of individual waste disposal situations, none of them addresses the dual task of developing and/or enlarging a salt cavern while simultaneously disposing of waste in the cavern so as to accelerate the overall process under conditions that minimize the capital investments and operating costs required to conduct these operations. A need exists to provide a safe and efficient method for developing and enlarging a salt cavern by solution mining techniques while simultaneously disposing of waste in the cavern under conditions that minimize the capital investments and operating costs required in carrying out such operations. The present invention is directed toward providing such a method.
It is an object of this invention to provide a method for the efficient deposition of materials and disposal of wastes in subterranean reservoirs. It is also an object of this invention to provide a method for the disposal of waste in subterranean formations under conditions that minimize the capital investments and operating costs required in carrying out such waste disposal operations. It is another object of this invention to provide a commercially efficient technique for the simultaneous creation of an underground salt cavern and disposal of waste generated in the natural resource mining industry. A further object of the invention is to provide a commercially efficient technique for enlarging and developing existing underground salt caverns while simultaneously disposing of oil field waste and other solid and liquid wastes in such existing underground salt caverns. A specific object of this invention is to provide a commercially efficient method for the development of new underground salt caverns and the enlargement and further development of existing underground salt caverns so that they may be effectively used for disposal of various kinds of solid and liquid wastes, which method is not only cost-effective but also environmentally sound. These and other objects of the present invention will become apparent from the description that follows.